dynamic modeling

Piezoelectric dispensers are widely applicable devices across many industries. However, their electromechanical structure often poses complexity in dynamic modeling. The interplay of many components especially compliant mechanisms and piezoelectric actuators makes modeling of the system challenging. In this study, the components of the system have been modeled individually and coupled together to predict the system behavior. For analyzing the bridge-type compliant mechanism, an appropriate method is proposed to model the structure with limited states. The mentioned method can predict the component behavior without sacrificing the precision which makes it ideal for coupling with other components' dynamics. Additionally, a non-linear modeling approach is introduced to capture the piezoelectric non-linear hysteresis behavior. Finally, by coupling the whole system dynamic, a comprehensive model is reached. The model developed for the compliant mechanism is individually validated by FEM software and experiments to prove the accuracy. The hysteresis nonlinear model is also identified and validated with the experiments with R squared exceeding 0.98. The entire coupled dynamics of the electromechanical system are identified and tested across several input frequencies. R-squared values exceed 0.95 for all input frequencies, affirming the accuracy of the dynamic model. Overall, the developed model is functional in the design and optimization of piezoelectric dispensers, as well as in automatic control system designs.

This research aims to model the nonlinear dynamics of the space propulsion system equipped with an electro-pump. For modeling, this system includes the combustion chamber, fuel and oxidizer tanks, and the corresponding pressurization system. A set of governing equations has been modeled in the Simulink of MATLAB software. The results of the modeling including changes in the angular velocity versus the time, changes in combustion chamber pressure versus the time, and changes in the mass flow rate of the fuel and oxidizer to the combustion chamber versus the time, are presented. In the end, the obtained results are compared with the results of the available engine and in addition to validating the results, it is possible to confirm and validate the performance of the electro-pump in a liquid fuel engine. The results showed that the angular velocity rate, the average acceleration rate of the combustion chamber, the average flow rate of the oxidizer to the combustion chamber and the average flow rate of the fuel to the combustion chamber obtained from the simulation and the available reference have a maximum error of 20%. The amount of difference in the conceptual design stage is free of problems. In addition, the trend of the graphs is similar.

Pneumatic Soft bending actuators as safe and highly adaptable robots are being considered by researchers, such that they become an ideal choice for making devices that interact more with humans. These advantages come along with several disadvantages. Their great adaptability is provided by their high degrees of freedom, and consequently, it makes the modeling a significant challenge for researchers. In this paper, the modeling of a soft fiber-reinforced bending actuator that is in contact with the environment has been conducted by utilizing the finite rigid element method. This method provides a context within which the modeling theories of traditional rigid robots, such as the Denavit-Hartenberg method, become usable for a soft continuum actuator. Therefore, in the following, resorting to this theory, the static and dynamic behavior of a soft actuator under the effect of the external load has been investigated and compared with the empirical results derived from a fabricated actuator. The results show a minimum accuracy of 9 percent, although being as simple as can be used for other purposes like implementing control systems based on that.

As a subset of mobile robots, the tractor-trailer mobile robot has been widely used in various applications in the past decades, including military and civilian missions, due to its advantages, such as a more expansive working space, high maneuverability, and load-carrying capacity has been used. One of the main challenges in controlling the tractor-trailer robot's speed is the tractor drives' dynamics. In this article, to complete the modeling after investigating the kinematic and dynamic equations governing the tractor-trailer robot, coupled dynamics have been presented by considering the dynamics of the tractor wheels. In the following, using the coupled dynamics, a suitable controller has been designed to control the robot's speed to achieve the desired value and the position point by point. Various simulations are presented to demonstrate the dynamic performance and the proposed controller. According to the simulation results, the presented theory improves the performance of the designed control system.

The design of a controller for a thrust vector control system of UAV has been studied through the robust  H∞ control method. In the first, the governing space-state equations of the system have been derived using the bond graph approach. Then, the critical performance parameters of the system were evaluated and identified according to the operational feasibility and the range of successful performance of the system. Next, the weight functions of the robust H∞,including the indeterminate weight function under the influence of specified uncertainties, were determined. Finally, the consistency of robust control in the presence of uncertainties was evaluated and the results of deflection of thrust vectoring nozzle were compared with the performance results of an optimized PID controller. The simulation results are determined using the MATLAB environment. The results of this study showed that the bond-graph method has good validity for modeling of this system and the designed robust controller can also meet its mission requirements

Due to the limited resources of fossil fuels and the pollution caused by them, the use of clean fuels seems necessary. In this regard, the development of electric or hybrid vehicles has great importance. In recent years, research areas related to autonomous electric vehicles have attracted the attention of automotive researchers and industrialists. These cars have different categories in terms of capabilities, including intelligent vehicle speed control. In this paper, dynamic modeling and longitudinal speed control of a level-one autonomous electric vehicle using GT-SUITE and MATLAB are investigated. Also, the model created in GT-SUITE software is validated with the help of data obtained from open-loop experimental tests. Then, after connecting the two software, the proportional-integral controller is designed to control the longitudinal speed of the vehicle and its parameters are adjusted.  Finally, the performance of the designed controller in controlling the vehicle speed in the presence of various conditions (road slope, wind blowing, and different velocity reference inputs) is evaluated.

This paper focuses on 3-D dynamic modeling of a transport quadrotor with cable in the presence of load generating stochastic forces. In many practical cases, we are dealing with payloads that generate oscillating forces with random amplitude and frequency by their inherent dynamics or interacting with the environment. These forces can greatly affect the dynamics of the transport system. The innovation of the present study is to consider these forces and show their impact on quadrotor’s dynamics. Furthermore, in order to make the model more compatible with the real system, it is assumed that the connection point of cable and quadrotor is not located on the center of gravity of flying vehicle and the cable's inertia is considered in the modeling process. To this end, the systems’ equations of motion are derived based on both Euler-Lagrange and Newton-Euler methods. After obtaining equations of motion, the verification of the model is investigated in three steps. In the first step, by performing simulation, the validity of the nonlinear model is investigated and dynamical analysis is expressed. In the next step, by evaluating the structure of the model, it is shown that the equations of motion satisfy some structural features of a desirable dynamic model. Then, by setting some parameters and variables to zero, it is shown that simpler models provided in some references can be achieved from this comprehensive model. At the end, the conclusion of this work is presented.

The effect of climatic and climatic changes in different geographical areas on the types of plants, animals and objects and the importance of protecting the items has led to the study of ideas related to control of air variables in desired conditions. All of the ideas studied in this field lead to the separation of under the control area in order to reduce the effect of the environment on the control variables. This area is then modeled as a system with a defined energy and mass exchange with the environment. In the present study, thermal modeling, dynamic modeling, and control of the variables of a museum which is considered an enclosed area have been investigated. For dynamic modeling, the one-dimensional heat transfer method is used for area elements (DETECt 2.3.1 method). After dynamic modeling, temperature and humidity control have been done using model-reference and modified adaptive methods. Numerical simulation results include the behavior of the system with and without using the controller, the variation of the dynamic variables, and changes in the control signal and the adaptive gains. The results show the success of control methods in the control of temperature and humidity of the studied area.

In this paper nonlinear dynamic behavior of bending actuators of dielectric elastomer or Dielectric Elastomer Minimum Energy Structure (DEMES) is studied and the effects of viscoelasticity of dielectric film on system response are investigated. Considering hyper-elasticity and viscoelasticity of dielectric film, the equation of motion of the actuator is extracted using Euler-Lagrange method. The natural frequency of small amplitude oscillations around the equilibrium state is calculated by linearizing the original nonlinear equation and the effects of dielectric film pre-stretch and excitation amplitude on natural frequency is investigated. The numerical simulation of the nonlinear equation of motion for periodic excitation shows that the system possesses harmonic resonances as well as sub-harmonic and super-harmonic resonances. By increasing the damping ratio of the dielectric film, resonance frequency increases for all harmonics and their excitation amplitude decreases. The analytical results show that excitation amplitude of harmonic resonance in chaotic behavior changes to a quasi-alternate and then an alternative behavior by increasing damping ratio.

Due to the high length to diameter of the tool and its high flexibility, internal turning process is very prone to chatter vibrations. Different methods have been used to increase dynamic stiffness of tools; the most effective method is active control method. In order to analyze and design a control system, a dynamic model of the system is required. Obtaining a system model using finite element modeling technique is complicated and time-consuming, thus, a method that can quickly and accurately estimate the response of the vibration control system is very important. The aim of this study is to propose a method for dynamic modeling of the internal turning tool using the experimental modal analysis, which can be used to predict and simulate vibration reduction. In this method, using the experimental modal test, a linear matrix model of the system dynamics was extracted and then the actuator-tool model was identified using sweep frequency method. Thereafter, by using the obtained models, the active vibration control loop of the internal turning tool was simulated in MATLAB/SIMULINK software and the controller performance was investigated. Finally, the simulation results were compared with the experimental results, which indicate good performance of the proposed method for dynamic modeling of the system and controller design. The proposed method in the identification frequency range accurately estimated the system response, and this method can be used to optimize the controller's gain.

Piezoelectric bending actuators have been extensively utilized in recent years. Two major modeling methods, lumped and continuous, have been generally proposed in previous researches for these actuators. The lumped method can only express the transverse vibration of one specified point on the actuator. In addition, the effect of higher vibrational modes has been ignored. Hence, continuous dynamic models have been proposed to rectify the mentioned drawbacks. In this method, linear constitutive equations for low voltage applications are usually applied. But, the main challenge in continuous modeling of piezoelectric actuators is the hysteresis nonlinear phenomenon caused by excitation voltages. In this paper, piezoelectric nonlinear constitutive equations have been employed to carry out the continuous dynamic model for two general types of bending actuators i.e. Series and Parallel. In addition, zero dynamic analysis for nonlinear systems has been applied to clarify the effect of higher vibrational modes the actuator dynamic behavior based on the location of Experimental results show the maximum error 1.44 and 1.2% in the identification of first and second modes, respectively, and the maximum error 2.89% in the modeling of actuator nonlinear behavior by two modes. These results validate the efficiency of the proposed dynamic model to express the actuator nonlinear behavior, dynamic analysis, and its superiority over conventional models with one mode.

Drying process demands high power consumption due to the low efficiency of this process in the industries. Therefore, modeling and simulation of dryers in order to optimize them and to design more efficient dryers is necessary. In this research, a cross-flow fluidized bed dryer has been simulated in order to evaluate a new design of the dryer. A mathematical model has been used to predict outlet solid moisture and temperature as well as outlet air humidity and temperature of a single story fluidized bed. The simulation results were evaluated using the experimental data of a pilot cross flow fluidize bed dryer. The comparison showed that the model can reasonably predict the process. Therefore, the simulation was used to investigate a new design of three story dryer (three sequential single story dryers). The simulation results showed while inlet solid moisture was 0.32 and outlet solid moisture for the single-story dryer was 0.19, in the same conditions, outlet solid moisture for the three-story dryer was 0.13. This means the new design can reduce solid moisture by 50 percent more, indicating the better use of hot air and subsequently more energy saving.

External disturbances and internal uncertainties with an unknown range, as well as the connection between the human body and robot, are major problems in control and stability of exoskeleton robots. In order to deal with disturbances and uncertainties with the known range of the system, the sliding mode controller is used as a robust approach. The chattering phenomenon is one of the drawbacks of sliding mode controller, which boundary layer is employed to reduce the effects of this phenomenon. In this case, not only the chattering phenomenon is not completely eliminated, but the robust characteristics of the controller are mitigated. In this paper, in order to cope with the disturbances and uncertainties with unknown range, and guard against chattering as a key ingredient of excessive energy consumption and convergence rate reduction, optimal adaptive high-order super twisting sliding mode control has been applied. The dynamic model of a lower limb exoskeleton robot is extracted using the Lagrange method in which four actuators on the hip and knee joints of the left and right legs are considered. To achieve optimal performance, controller parameters are determined using Harmony Search algorithm by minimizing an objective function consisting of ITAE and control signal rate. The proposed controller performance is compared with optimal adaptive supper twisting sliding mode and optimal sliding mode controllers which shows the superiority of the optimal adaptive high-order sliding mode controller rather than other designed controllers.

In this paper, an optimal robust nonlinear model predictive controller based on harmony search algorithm is designed for a type of 3-DOF translational parallel robot. Dynamic model of the mechanism is derived using Lagrange method and the model predictive controller augmented by uncertainty estimator is designed and stability is proved by Lyapanov theorem. Performance of the designed controller is evaluated in different conditions such as presence of disturbance and parameter variation. Furthermore, an optimal trajectory consisting four circular obstacles is designed as the reference trajectory of the robot. In order to obtain the optimum control parameters, a cost function combining control signal rate and error is considered and minimized by harmony search algorithm. In order to compare the performance of the designed controller with other nonlinear controllers, two controllers, an optimal sliding mode and a feedback linearization controller are also designed and their results are compared. Simulation results depict the desirable performance of the three controllers in spite of disturbance and model uncertainty, however, error criteria indicate priority of the robust nonlinear model predictive controller over the two other controllers.

The purpose in this paper is to express a suitable process of modeling and simulation of a ballistic launch vehicle and introducing necessary mathematical solutions for the process. This vehicle is a three – stage ballistic launch vehicle such that each stage has independent condition and characteristic such as mass characteristic, aerodynamic characteristic, propulsion characteristic and control characteristic. The suitable coordinate systems are introduced and analyzed for modeling, such as inertial coordinate system, earth coordinate system, navigation coordinate system and body coordinate system. The equation of motion of this ballistic launch vehicle with respect to earth frame and navigation frame are considered and transformation matrices are mentioned to express definition of vectors in coordinate systems. In this procedure the earth is modeled as an ellipsoid surface with a gravitational field model according to World Geodetic System 1984. Avoiding singularity, quaternions are considered as rotational states instead of Euler angles. Finally, the results of simulation are presented and analyzed graphically.

In this paper, an optimal adaptive sliding mode controller of an Omni-Directional Mobile Robot (ODMR) is proposed using harmony search algorithm. First, kinematic model of the robot is derived and then, governing equations of dynamic model have been obtained using linear and angular momentum equilibrium. Since the derived model is not an exact definition of the system, it includes some uncertainties. To compensate them, a tracking control method has been offered. The proposed controller consists of an approximately known inverse dynamic model output as the model-based part of the controller, an estimated uncertainty term to compensate for the un-modeled dynamics, external disturbances, and time-varying parameters to enhance closed-loop stability and account for the estimation error of the uncertainties. In order to compare the results of the proposed controller, an optimal feedback linearization and sliding mode controllers are designed and then, a cost function has been defined by combining the variation rate of control signal and the integral error index. This cost function has been minimized using harmony search algorithm, resulting in optimum control parameters. Finally, the performance of the designed controller in different conditions, such as in presence of disturbance and system parameter variation has been simulated and discussed.

According to numerous capabilities and increasingly military and commercial applications of radio controlled helicopters, many investigations are being performed on these unmanned aircraft vehicles. Due to nonlinear, complex, unstable and coupled dynamic system and also existing limitations on manual control, the ability of automatic control of these vehicles has gained great importance. In this paper, in addition to investigating different methods of unmanned helicopters dynamic modeling, a multi-level simulator environment has been designed and implemented for flight performance analysis and effects of different parameters have been investigated. The main importance and innovation of present simulator is in possibility of dynamic flight simulation of helicopter using different theories for applications like control system design, performance analysis and real flight simulation. The main difference of the utilized methods is in theories and assumptions applied in main rotor and its flapping dynamics modeling. For each level, Kalman filter and control system design have been performed and preliminary results show the acceptable performance of estimator and controller systems. Considering the complexity of real unmanned helicopter behavior compared to previously performed models, the proposed multi-level simulator can be used as an appropriate tool for the first step before real flight tests.

To get the real answer a PEM fuel cell system to load changing, dynamic modeling is necessary because static modeling independent of time and it shows the system performance in just one or a few points. In this study, the dynamic performance of a PEM fuel cell stack is modeled in the Matlab Simulink and is validated by the data available in the literature. Modeling is done in two parts; in the first part, the input gases to the fuel cell stack are dray and the second part, the gases entering to the stack are humidification. In order to investigate dynamic response of system to rapid changes in electrical current, the variable electrical current is entered into the system step by step then the effect of this change on output voltage, consumption of reactants, temperature and pressure are obtained. Analyzing results of first part indicates that the time delay of system response to electrical current changes. With increasing the electrical current, the temperature of cell body, consumption of reactants and amount of input gases into the anode and the cathode channels are increased. The temperature of anode and cathode channels and fuel cell body are different and with increasing the stack power are more differences. Analyzing the results of second part indicates that with increasing the relative humidity of input gases the ohmic loss and so on the body temperature of fuel cell is decreased.